The present invention relates in general to a method for fabricating a mesh of a tetraode field-emission display, and more particular, to a method for fabricating a mesh combining a converging electrode layer, an insulation layer and a gate layer.
The field-emission display is a very newly developed technology among flat panel display field. Being self-illuminant, such type of display does not require a back light source like the liquid crystal display. In addition to the better brightness, the viewing angle is broader, power consumption is lower, response speed is faster (no residual image), and the operation temperature range is larger. The image quality of the field-emission display is similar to that of the conventional cathode ray tube (CRT) display, while the dimension of the field-emission display is much thinner and lighter compared to the cathode ray tube display. Therefore, it is foreseeable that the field-emission display may replace the liquid crystal display in the market. Further, the fast growing nanotechnology enables nano-material to be applied in the field-emission display, such that the technology of field-emission display will be commercially available.
FIG. 1 shows a conventional triode field-emission display, which includes an anode plate 10 and a cathode plate 20. A spacer 14 is placed in the vacuum region between the anode plate 10 and the cathode plate 20 to provide isolation and support thereof. The anode plate 10 includes an anode substrate 11, an anode conductive layer 12 and a phosphor layer 13. The cathode plate 20 includes a cathode substrate 21, a cathode conductive layer 22, an electron emission layer 23, a dielectric layer 24 and a gate layer 25. A potential difference is provided to the gate layer 25 to induce electron beam emission from the electron emission layer 23. The high voltage provided by the anode conductive layer 12 accelerates the electron beam with sufficient momentum to impinge the phosphors layer 13 of the anode plate 10, which is then excited to emit a light. To allow electron moving in the field-emission display, the vacuum is maintained at least under 10−5 torr, such that a proper mean free path of the electron is obtained. In addition, contamination and poison of the electron emission source and the phosphors layer have to be avoided. Further, the electron emission layer 23 and the phosphors layer 13 have to be spaced from each other by a predetermined distance for accelerating the electron with the energy required to generate light from the phosphors layer 13.
The electron beam emitted by the conventional structure is typically in a fan configuration, and the diverging range of such electron beam is difficult to control by the triode field-emission display. The electron beam is easily excessively divergent and may even impinge the phosphors layer 33 of the neighboring unit to degrade the display effect. Therefore, a tetra-polar structure is proposed as shown in FIG. 2. In the tetra-polar structure, a fourth electrode, that is, the converging electrode is formed in addition to the triode structure. A mesh 5 is formed between the cathode plate 40 and the anode plate 30. The mesh 5 includes a converging electrode layer 51, an insulation layer 52 and a gate layer 53. The converging electrode layer 51 is proximal to the anode plate 30, the gate layer 53 is proximal to the cathode plate 40, and the insulation layer 52 is sandwiched between the converging electrode layer 51 and the gate layer 53. An isolation wall 44 is formed to extend between the gate layer 53 and the cathode layer 40. The cathode plate 40 includes a cathode substrate 41, a cathode conductive layer 42 and an electron emission source layer 43. The gate layer 53 and the converging electrode layer 51 carries adequate potentials. A plurality of apertures 54 is formed to extend through the mesh 5. Each of the apertures 54 is aligned with a corresponding unit of anode and cathode, such that electron beam generated from the electron emission source layer 43 can propagate towards the phosphor layer 33.
Practically, due to the divergence of the electron beam, the apertures 54 of the mesh 5 are modified as shown in FIG. 3. That is, the first aperture 511′ of the converging electrode layer 51′ is larger than the second aperture 521′ of the insulation layer 52′ and the third aperture 531 ′ of the gate layer 53′. In fabrication, a metal conductive plate is used as a base of the mesh 5. That is, the converging electrode layer 51 fabricated from the metal conductive plate. The insulation layer 52 is formed on the bottom surface of the metal conductive layer. A conductive layer is then formed on the bottom surface of the insulation layer 52 to serve as the gate layer 53. The metal conductive plate is processed to form an array of first through apertures 511′. The position of each first aperture 511 ′ is aligned with each unit of anode and cathode formed on the anode and cathode plates 30 and 40, respectively. The apertures 54 serve as emission channel for the electron beam emitted from each cathode.
The above tetraode structure provides the converging electrode layer 51 to converge the electron beam, such that the electron beam can impinge the corresponding phosphors layer 33 precisely. Therefore, the electron beam is prevented from impinging the phosphor layer 33 of the neighboring units. The display effect of the field emission display is thus greatly enhanced. However, as the insulation layer 52 and the gate layer 53 are still fabricated by screen printing, the disadvantages are existed as follows.
First, as shown in FIG. 3, since the first aperture 511′ of the converging electrode layer 51′ is larger, when printing the insulation layer 52′ and the gate layer 53′, the peripheries of the second aperture 521′ and the third aperture 531′ may be damaged.
Second, since the existence of the first aperture 511′, when printing the insulation layer 52′ and the gate layer 53′, the first aperture 511 ′ may be contaminated by applying a glass glue coating of the insulation layer 52′, and the conduction between the gate layer 53′ and the converging electrode layer 51′ may be blocked by applying a silver glue coating of the gate layer 53′.